It's no joke to the health care system, though. Repeat customers to hospitals are seen as a big problem. But it's complicated. Sometimes the hospitals themselves may profit from some patients' frequent visits. But it costs a lot money for the people who pay hospitals: Medicare, Medicaid and private insurers.

As with many other problems in the health care system, unnecessary hospital readmissions are associated with worse treatment and health outcomes as well as higher costs to taxpayers — as much as $17 billion a year by one estimate.

Starting next fall, the Department of Health and Human Services will begin penalizing hospitals if their Medicare readmission rates are higher than expected for three conditions: heart attacks, heart failure and pneumonia. In the first year that penalties kick in, 1 percent of hospitals' a Medicare payments will be withheld, and the amount will increase in subsequent years.

Hospitals are working on ways to combat readmissions. On a recent weekday, Josuely Claudio, visited a clinic at Mount Sinai Hospital in New York that targets patients with complicated, chronic health problems who come in way too often.

The 53-year-old has congestive heart failure, diabetes, high blood pressure and a stomach problem that makes him gag almost constantly. "Sometimes I dehydrate, and I don't know if it's my blood glucose or high blood pressure, low blood pressure," Claudio says.

He was inconsistent about taking insulin and various medications, keeping doctors' appointments and maintaining a healthful diet. So when Mt. Sinai created its Preventable Admissions Care Team, or PACT, last year, Claudio was a natural candidate. He joined in late 2011 and has had biweekly visits to the clinic.

Usually he meets with a social worker and nurse practitioner, and occasionally sees a doctor. The idea of this transitional care is to make patients more self-sufficient and not wind up in the emergency room.

Mt. Sinai's readmission rates for heart failure are among the worst in the nation. Hospital administrator Claudia Colgan challenges how the federal data on readmissions are gathered, but she concedes that getting readmissions down is a top priority. It will take a major "culture shift" to do it, she says.

Historically, readmissions have been lucrative for Mt. Sinai — and for many hospitals.

Sure, paying for avoidable care might be bad, if you're the government or a private insurance company. For those being paid, repeat customers like Claudio are money in the bank. Dr. Eric Coleman, from the University of Colorado, says for too long hospitals have benefited from a system that rewards them for excessive care. A hospital might get 15 to 25 percent of its revenue from readmissions.

But Dr. Ashish Jha, in the latest New England Journal of Medicine, argues readmissions aren't the best indicator of unnecessary care — even though they're an easy target for budget-cutters. The Harvard University professor notes many of the hospitals with the highest readmission rates also serve the poorest areas with the biggest health problems.

"Readmissions are caused by what hospitals do, who the patients are, and what's happening in the community," he says. "You want hospitals to fix the things they can, but you don't want to punish them for taking care of poor people, and you don't want to punish them for being located in a poor area."

There are some signs Mt Sinai's work is getting results. In the program's first full year, its 500 patients have had a 40 percent drop in readmissions and a 55 percent drop in emergency room visits.

In the 12 months before he joined the PACT program, Josuely Claudio had 20 emergency room visits and overnight admissions. Mt. Sinai billed Medicare almost $140,000 for his treatment. In the last 12 months, he's had seven emergency room visits and overnight admissions, costing taxpayers a little more than $54,000.

Mt. Sinai is absorbing almost all of the costs of those twice-a-week clinic visits. The PACT program this year will cost the hospital about $1 million, and it's not clear how long Mt. Sinai can foot the bill for PACT — especially, if it turns out to be cheaper just to pay the penalty.

This story by Fred Mogul is part of a reporting partnership that includes WNYC, NPR and Kaiser Health News.